Various forms of apparatus have been proposed in the luminaire art to achieve control of radiant energy. One form comprises a rotatable structure having multiple filters for producing changes in color. This rotatable structure is commonly referred to in the art as a "color wheel". Another form of apparatus consists of a housing having a reflector body and an energy source movable with respect to one another. This apparatus may be utilized to produce either a spot distribution or a defocused annular distribution of emitted radiant energy.
Still another well known form of apparatus of the class noted consists of an opaque iris-type device which is used to vary the size of an aperture through which radiant energy may be omitted from a luminaire body.
All of these prior art systems are subject to certain disadvantages. The "color wheel," for example, does not readily allow changes in color to take place progressively from the edges of a light pattern towards its center which is extremely desirable for highlighting subject matter. Where an energy source and a deflector body, movable with respect to one another, are employed it is not possible to produce an even flood distribution. Use of an opaque iris-type diaphragm is extremely inefficient when utilized to produce a spot configuration since a large percentage of available radiant energy will be excluded by the opaque iris.